In recent years, sugar chain engineering has been remarkably developing and has been revealing the mechanisms where sugar chains in macromolecules such as plant cell wall proteoglycans contributing to stabilization of cells, glycolipids having an influence on the differentiation, growth, adhesion and movement of cells, and glycoproteins involved in intercellular interaction and recognition of cells regulate highly accurate biological reactions with their functions mutually exchanged, assisted, amplified, controlled or inhibited. Sugar chains on cell surfaces, occurrence of diseases due to an abnormality in sugar chain/receptor interaction, or the role of sugar chains in viral infection such as AIDS are being extensively studied.
Particularly, sugar chains that cells have on their surfaces can be utilized for discriminating and identifying certain cells from other cells, for example normal cells from cancer cells, or different cells in their differentiation stage. For example, there have been many reports that sugar chains varies in cancer cells depending on their malignancy, or varies in stems cells depending on their differentiation stage. Accordingly, the analysis (e.g. discrimination and identification) of sugar chains is considered very important in distinguishing, identifying and fractionating cells.
Utilization of lectins having a binding activity to specific sugar chains (carbohydrates) is considered to bring many merits as a means of analyzing carbohydrates on cell surface, represented by such sugar chains. However, at present, the type of naturally occurring lectins is limited, and there are not utilized enough types of lectins for analyzing particularly sugar chains as described above. That is, discriminating subtle differences in sugar chains, etc., is very important in analysis of carbohydrates, including analysis of sugar chains. Therefore, it is a key task in this analysis that various kinds of lectins having specificities to enable discrimination of carbohydrates can be prepared sufficiently and systematically.